A rapid redistribution of hydrogen ions is associated with depolarization and repolarization subsequent to cerebral ischemia reperfusion

A rapid redistribution of hydrogen ions is associated with depolarization and repolarization... Abstract 1. The aim of this study was to examine the rapid changes in extracellular hydrogen ion activity ( H+o or pHo) which are associated with depolarization and repolarization subsequent to cerebral ischemia reperfusion. Two parallel studies were performed with different rat models of ischemia: repetitive severe ischemia produced in anesthetized animals by occlusion of the vertebral and carotid arteries and temporary interruption of blood flow in isolated brain. H+o and direct current potential (DC potential) were recorded simultaneously in all experiments. Examination of these two parameters was supplemented by recording tissue concentration of carbon dioxide (PtCO2) in the four-vessel occlusion model and assaying major metabolites involved in energy production in experiments with isolated brains. 2. Measurements of H+o during ischemia consistently revealed a steady increase of H+o on which was superimposed an abrupt and transient fall in H+o closely related to the occurrence of the fast negative shift of DC potential characterizing brain-cell depolarization. Analysis of the relationship between the magnitude of the transient fall in H+ and the level of H+o at which this occurred showed that the amplitude of the transient fall in H+ increased with tissue acidosis. 3. We propose that this phenomenon is indirect evidence that rapid transfer of acid equivalents occurs across the plasmalemma, concomitantly to its depolarization. Both events probably result from a common cause, i.e., nonspecific increase of the cell-membrane permeability to ions subsequent to opening of membrane channels. 4. Early on during recirculation, an acidotic H+o shift associated with membrane repolarization was clearly visible whenever the ionic gradients recovered rapidly.(ABSTRACT TRUNCATED AT 250 WORDS) Copyright © 1990 the American Physiological Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Neurophysiology The American Physiological Society

A rapid redistribution of hydrogen ions is associated with depolarization and repolarization subsequent to cerebral ischemia reperfusion

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Publisher
The American Physiological Society
Copyright
Copyright © 1990 the American Physiological Society
ISSN
0022-3077
eISSN
1522-1598
Publisher site
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Abstract

Abstract 1. The aim of this study was to examine the rapid changes in extracellular hydrogen ion activity ( H+o or pHo) which are associated with depolarization and repolarization subsequent to cerebral ischemia reperfusion. Two parallel studies were performed with different rat models of ischemia: repetitive severe ischemia produced in anesthetized animals by occlusion of the vertebral and carotid arteries and temporary interruption of blood flow in isolated brain. H+o and direct current potential (DC potential) were recorded simultaneously in all experiments. Examination of these two parameters was supplemented by recording tissue concentration of carbon dioxide (PtCO2) in the four-vessel occlusion model and assaying major metabolites involved in energy production in experiments with isolated brains. 2. Measurements of H+o during ischemia consistently revealed a steady increase of H+o on which was superimposed an abrupt and transient fall in H+o closely related to the occurrence of the fast negative shift of DC potential characterizing brain-cell depolarization. Analysis of the relationship between the magnitude of the transient fall in H+ and the level of H+o at which this occurred showed that the amplitude of the transient fall in H+ increased with tissue acidosis. 3. We propose that this phenomenon is indirect evidence that rapid transfer of acid equivalents occurs across the plasmalemma, concomitantly to its depolarization. Both events probably result from a common cause, i.e., nonspecific increase of the cell-membrane permeability to ions subsequent to opening of membrane channels. 4. Early on during recirculation, an acidotic H+o shift associated with membrane repolarization was clearly visible whenever the ionic gradients recovered rapidly.(ABSTRACT TRUNCATED AT 250 WORDS) Copyright © 1990 the American Physiological Society

Journal

Journal of NeurophysiologyThe American Physiological Society

Published: Oct 1, 1990

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